Hitherto a process for granulating a polytetrafluoroethylene granular powder for molding by using an organic liquid and tumbling a powder has been proposed. For example, JP-B-45-9071 discloses a process for tumbling a powder while heating the powder, JP-B-44-22620 discloses a process for granulating by tumbling for obtaining a filler-containing PTFE granular powder, and JP-B-46-14535 discloses a process for granulating by tumbling with a pan type pelletizer.
However, the processes disclosed in those publications have problems such that an organic liquid used is inflammable and harmful to human body and further that equipment cost for carrying out the processes becomes high.
An object of the present invention is to provide a polytetrafluoroethylene granular powder for molding, which contains only a small amount of coarse particles, and a process for preparing the granular powder at high yield with good tumbling efficiency without necessity of using an organic liquid.